Multistage compressor

ABSTRACT

A multistage compressor may have at least one high-pressure stage and at least one low-pressure stage. The compressor may also include at least two pistons, which are driven via a common crankshaft supported in a crankcase, and which may be guided in associated cylinders, and which may form the at least one high-pressure stage and the at least one low-pressure stage. The compressor may further include a line arrangement which may communicate with the each of the cylinders for supplying and discharging air to and from the cylinders. There may be arranged in the line arrangement a switchable valve, which may be constructed in such a manner that the at least one high-pressure stage depending on a switching position of the valve may be associated with a different one of the cylinders.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Patent Application No. PCT/EP2018/057058, filed on Mar. 20, 2018, and German Patent Application No. DE 10 2017 205 366.6, filed on Mar. 29, 2017, the contents of both of which are hereby incorporated in their entirety.

TECHNICAL FIELD

The present invention relates to a multistage condenser. The invention further relates to a compressor having such a multistage condenser and an operating method of such a multistage condenser.

BACKGROUND

Multistage condensers or multistage compressors are sufficiently known and generally have at least one low-pressure stage and one high-pressure stage, wherein the high-pressure stage is subjected to a higher level of wear and thereby often represents a weak point of such a multistage condenser.

Multistage condensers may, for example, have a plurality of piston/cylinder units, of which, for example, one piston/cylinder unit forms a high-pressure stage and one piston/cylinder unit forms a low-pressure stage. In the low-pressure stage, in this instance the gas which is intended to be compressed, for example air, is (pre-) compressed at a first pressure stage and subsequently supplied to the at least one second piston/cylinder unit, consequently the high-pressure stage. In between there may of course also be a charge air cooler.

However, the disadvantage of multistage condensers known from the prior art is that in particular the piston rings in the high-pressure stage become more quickly worn as a result of the higher loading so that a failure of the multistage condenser may occur even when low-pressure stages are still working correctly purely as a result of a worn high-pressure stage.

SUMMARY

The present invention therefore addresses the problem of providing a multistage condenser which overcomes the disadvantages known from the prior art.

This problem is solved according to the invention by the subject-matter of the independent claims. Advantageous embodiments are set out in the dependent claims.

The present invention is based on the general notion of providing a multistage condenser having at least one high-pressure stage and having at least one low-pressure stage, which is switched during operation in such a manner that not only a single piston/cylinder unit always forms the high-pressure stage, but instead the high-pressure stages moves over all the piston/cylinder units, whereby a uniform wear and consequently a longer service life can be achieved. To this end, there is used a so-called “cyclical” valve device which depending on the switching position with each cycle transmits the high-pressure stage one position, that is to say, allocates it to a following piston/cylinder unit. The multistage condenser according to the invention has in this instance at least two pistons which are driven by means of a common crankshaft, which is supported in a crankcase, and which are guided in associated cylinders of a respective piston/cylinder unit and which form the at least one high-pressure stage and the at least one low-pressure stage. Of course, in this instance a total of three or more piston/cylinder units may also be provided, of which one in each case forms a high-pressure stage and the two or more others form the upstream low-pressure stages. There is further provided a line arrangement which communicates with the individual cylinders in order to supply and discharge air to and from the individual cylinders. In this line arrangement there is arranged according to the invention the switchable valve device, which is constructed in such a manner that the high-pressure stage depending on the switching position is associated with different cylinders, in particular in such a manner that the at least one high-pressure stage with each cylinder operating cycle moves one cylinder or one piston/cylinder unit further.

In this instance, it is also conceivable to change the high-pressure stage not for every operating cycle, but instead, for example, only for every tenth operating cycle. That is to say, over a time range t all the piston/cylinder units would still be loaded and therefore also worn in the same manner. A change of the high-pressure stage with each new warm-up/start of the compressor is also conceivable.

The valve device may in this instance be constructed mechanically, electrically, pneumatically or also in another manner. As a result of the embodiment of the multistage condenser according to the invention, it is possible to use piston/cylinder units with the same dimensions, whereas, for example, with multistage condensers known from the prior art, a high-pressure stage is in each case constructed with a smaller volume. As a result of the dimensions of the multistage condenser according to the invention being identical for the first time, standard components can be used, whereby the variety of components and consequently also the storage and logistics costs and the assembly costs can be reduced. Another advantage of the multistage condenser according to the invention is that, as a result of the moving high-pressure stage, the provision of highly compressed air is still possible even in the event of a failure of a piston/cylinder unit. This can be detected, for example, by means of corresponding sensors, whereupon a control of the multistage condenser no longer controls, and skips, the piston/cylinder unit which is damaged or no longer working correctly. In multistage condensers known from the prior art, a failure, for example, of the high-pressure stage always leads to the failure of the complete condenser.

In an advantageous development of the solution according to the invention, a pre-compression cooler which is arranged downstream of the at least one low-pressure stage and upstream of the at least one high-pressure stage is provided. Via such a pre-compression cooler, the thermal energy which is supplied to the air during compression can be discharged again, whereby a further compression is more readily possible. Of course, a high-compression cooler may also be arranged downstream of the high-pressure stage, for example, before the now highly compressed charge air is introduced into a pressure store, whereby the storage capacity can be increased.

In another advantageous embodiment of the solution according to the invention, a high-pressure stage and three low-pressure stages are provided as well as four pistons which are driven by means of a common crankshaft which is supported in a crankcase and which are guided in associated cylinders in associated piston/cylinder units and which form a high-pressure stage and three low-pressure stages. Such a condenser can be driven, for example, by means of an electric motor. Of course, in this regard, alternative embodiments of the multistage condenser according to the invention can also be considered, for example, having a total of five, six or more condenser stages, of which, for example, two function as high-pressure stages and the remainder as low-pressure stages. As a result of the fact that, in the multistage condenser according to the invention, all the condenser stages, that is to say, all the piston/cylinder units, have the same dimensions, almost any desired scaling is possible. If, for example, a higher volume flow is required, the number or the volume of the condenser units can be simply increased.

The present invention is further based on the general notion of providing a compressor, in particular an oil-free compressor, having a circuit described in the previous paragraphs, whereby an operating method which is durable and reliably functioning per se can be achieved since the multistage condenser according to the invention not only becomes less worn and is consequently longer-lasting, but purely theoretically using corresponding detection devices and sensors and control devices can also readily compensate for the failure of at least one pressure stage. The present invention is further based on the general notion of providing an operating method of the above-described multistage condenser, in which a switchable valve device is switched in such a manner that the high-pressure stage depending on the switching position of the valve device is associated with different cylinders, in particular in such a manner that the at least one high-pressure stage, with each operating cycle, that is to say, during an upward and downward movement of an associated piston in an associated piston/cylinder unit, moves one cylinder further. Also in this instance, it is conceivable to change the high-pressure stage not with every operating cycle, but instead, for example, only with every tenth operating cycle. That is to say, over a time range t, all the piston/cylinder units would still be loaded and therefore also worn in the same manner. As a result of the continuous movement of the at least one high-pressure stage, the signs of wear which previously occurred in only a single piston/cylinder unit which forms the high pressure-stage can now be distributed in a uniform manner over all the piston/cylinder units, whereby they are subjected to less wear and thereby on the whole a longer service life for the condenser is achieved.

Other important features and advantages of the invention will be appreciated from the dependent claims, from the drawings and from the associated description of the Figures with reference to the drawings.

Of course, the features mentioned above and those explained below can be used not only in the combination given in each case, but also in other combinations or alone, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and are explained in greater detail in the following description, wherein the same reference numerals refer to components which are identical or similar or which have the same function.

BRIEF DESCRIPTION OF THE DRAWINGS

In the schematic drawings:

FIG. 1 is a sectioned illustration through a multistage condenser according to the invention without a more detailed illustration of an associated valve device according to the invention,

FIG. 2 shows an associated valve device in a first switching position,

FIG. 3 is an illustration as in FIG. 2, with a valve device in a second switching position,

FIG. 4 shows a possible embodiment of a valve member of the valve device,

FIG. 5 shows an upper portion of the valve member in the intake cycle,

FIG. 6 shows a lower portion of the valve member in the exhaust cycle.

DETAILED DESCRIPTION

According to FIGS. 1 to 3, a multistage condenser 1 according to the invention has at least one high-pressure stage 2 and at least one low-pressure stage 3. According to FIG. 2, the multistage condenser 1 has a total of four pressure stages, of which one is constructed as a high-pressure stage 2 and three are constructed as low-pressure stages 3. Each pressure stage 2, 3 has in this instance an individual piston/cylinder unit 4 having a cylinder 5 and a piston 6 which is supported therein so as to be able to be adjusted in a translational manner, wherein the pistons 6 are driven by means of a common crankshaft 8 which is supported in a crankcase 7 (cf. FIG. 1). There is also provided a line arrangement 9 which communicates with the individual cylinders 5 for supplying and discharging air to and from the cylinders 5. In the line arrangement 9 (cf. in particular FIGS. 2 and 3) there is arranged according to the invention a switchable valve device 10 which is constructed in such a manner that the high-pressure stage 2 depending on the switching position of a valve member 11 of the valve device 10 is or becomes associated with different cylinders 5, in particular in such a manner that the at least one high-pressure stage 2 during each operating cycle of a piston 6 moves one cylinder 5 further. Alternatively, it is also conceivable to change the high-pressure stage 2 not for each operating cycle, but instead, for example, only for each tenth operating cycle. That is to say, over a time range t, all the piston/cylinder units 4 would still be loaded and therefore also worn in the same manner.

According to FIG. 2, in this instance, the valve device 10 is shown in an intake position in which the low-pressure stages 3 draw air from the crankcase 7 via the valve body 11 of the valve device 10. The intake can selectively also be carried out directly from the ambient air or an intermediate filter. In the same manner, air which has already been pre-compressed in a previous operating cycle and which is cooled via the pre-compressor cooler 12 is drawn and supplied via the valve body 11 of the valve device 10 of the high-pressure stage 2, that is to say, therefore, supplied to the piston/cylinder unit 4 which is depicted at the top left. In a next operating cycle, in the event of a consequently subsequent rotation of the valve body 11 of the valve device 10 in a clockwise direction, the high-pressure stage 2 would move from the top left to the top right and in the same manner the low-pressure stages 3 would be rotated about a piston/cylinder unit 4 in each case in a clockwise or counter-clockwise direction. Of course, other movements of the valve body 11 are also conceivable, for example, translational ones.

If FIG. 3 is viewed, it is possible to see an exhaust cycle, in which the pre-compressed air from the three low-pressure stages 3 is directed via the valve body 11 of the valve device 10 to the first pre-compression cooler 12. In the same manner, in the high-pressure stage 2 highly compressed charging air is supplied via the valve body 11 of the valve device 10, for example, to a second high-compression cooler 13 and/or finally to a pressure store 14. By rotating the valve body 11 in the clockwise direction or in the opposite direction, using the valve device 10 according to the invention and the associated line arrangement 9, a movement of the respective high-pressure stage 2 via the individual piston/cylinder units 4 is achieved, whereby the occurrences of wear which increasingly appear in the high-pressure stage 2 can be distributed in a uniform manner over all the piston/cylinder units 4 and whereby the service life of the multistage condenser 1 according to the invention is significantly increased.

According to FIG. 2, in this instance, for reasons of clarity, only the inlet lines of the line arrangement 9 in the respective piston/cylinder units 4 are illustrated, whilst, according to FIG. 3, only the outlet lines are illustrated. Of course, however, the line arrangement 9 still has an inlet and outlet line to and from the respective piston/cylinder unit 4.

In the condenser 1 illustrated in FIGS. 2 and 3, on the whole in each case three low-pressure stages 3 and in each case only a single high-pressure stage 2 are provided, wherein of course other low-pressure stages 3 or high-pressure stages 2 may also further be provided.

The multistage condenser 1 according to the invention is operated by the switchable valve device 10 being switched in such a manner that the high-pressure stage 2 depending on the switching position is associated with different cylinders 5, that is to say, different piston/cylinder units 4, so that the at least one high-pressure stage 2 for each operating cycle of the piston 6 or for each switching cycle of the valve device 10 moves one cylinder 5 or one piston/cylinder unit 4 further. Alternatively, it is also conceivable to change the high-pressure stage 2 not for every operating cycle but instead, for example, only for every tenth operating cycle. That is to say, over a time range t, all the piston/cylinder units 4 would still be loaded in the same manner and the increased occurrences of wear brought about by the high-pressure stage 2 can be transferred uniformly to all the piston/cylinder units 4. The multistage condenser 1 according to the invention further has the significant advantage that, for example, as a result of the failure of a single low-pressure stage 3, they can be switched off by identification, for example, by means of a corresponding control device so that the multistage condenser 1 according to the invention continues to operate even in the event of a failure of a single or a plurality of low-pressure stages 3 or high-pressure stages 2 since the high-pressure stage 2 is connected not only to a single but instead at least to fixed piston/cylinder units 4.

The valve device 10 has according to FIG. 4 a rotatable cylindrical valve body 11 having an upper portion 17 and a lower portion 18 and may be able to be switched pneumatically, electrically or hydraulically. In this instance, there are arranged in the valve body 11, on the covering face thereof, different inlets 15 or outlets 16 which depending on the switching position can also change their inlet function or outlet function. Of course, the inlets 15 and outlets 16 may also be arranged in a transposed manner.

According to FIG. 5, in this instance an upper portion 17 of the valve body 11 is shown in an intake position in which the low-pressure stages 3 draw air from the crankcase 7 or from the environment, in particular via a filter device. In this instance, an intake of air is carried out via three inputs 15 a. The drawn air is in this instance supplied via the outputs 16 a which are associated with the inputs 15 a to the piston/cylinder units 4 which are constructed as low-pressure stages 3 and after the compression cycle is supplied to the pre-compression cooler 12. The term “pre-compression cooler 12” in this instance refers to the cooling after the low-pressure compression and before the high-pressure compression. In the same manner, air which has already been pre-compressed in a previous operating cycle and cooled via the pre-compression cooler 12 is drawn via the inlet 15 b and supplied via the valve body 11 of the valve device 10 and the outlet 16 b associated with the inlet 15 b to the high-pressure stage 2, that is to say, therefore, the piston/cylinder unit 4 which is depicted at the top left.

If FIG. 6 is viewed, it is possible to see at that location a lower portion 18 of the valve body 11 during an exhaust cycle which is carried out at the same time as the intake cycle of the upper portion 17 and in which the now pre-compressed air from the three low-pressure stages 3 is directed via the inlets 15 a and the associated outlets 16 a of the valve body 11 of the valve device 10 to the first pre-compression cooler 12. In the same manner, charge air which has been highly compressed in the high-pressure stage 2 is supplied via the inlet 15 b of the valve body 11 of the valve device 10 and the associated outlet 16 b, for example, to a second high-compression cooler 13 and/or finally to a pressure store 14. By rotating the valve body 11 in a clockwise direction or in the opposite direction, using the valve device 10 according to the invention and the associated line arrangement 9, a movement of the respective high-pressure stage 2 via the individual piston/cylinder units 4 is achieved, whereby the occurrences of wear which increasingly appear in the high-pressure stage 2 can be distributed in a uniform manner over all the piston/cylinder units 4 and whereby the service life of the multistage condenser 1 according to the invention significantly increases.

The two portions 17, 18 can be rotated relative to each other or together. The intake cycle is controlled via the lower portion 17. The exhaust cycle is controlled via the upper portion 18 or vice versa. Both portions 17, 18 move simultaneously in a clockwise or anti-clockwise direction in order to enable precise timing with at the same time a robust construction. However, there is no connection of the channels or millings between the upper portion 17 and the lower portion 18.

The crankshaft 8 and consequently the multistage condenser 1 can be driven, for example, by means of an electric motor which is not shown. 

1. A multistage condenser, comprising: at least one high-pressure stage and at least one low-pressure stage; at least two pistons which are driven via a common crankshaft supported in a crankcase, and which are guided in associated cylinders, and which form the at least one high-pressure stage and the at least one low-pressure stage; a line arrangement which communicates with the each of the cylinders for supplying and discharging air to and from the cylinders; wherein there is arranged in the line arrangement a switchable valve, which is constructed in such a manner that the at least one high-pressure stage depending on a switching position of the valve device is associated with a different one of the cylinders.
 2. The condenser as claimed in claim 1, wherein the at least one high-pressure stage for each cylinder operating cycle or each switching position moves one cylinder further.
 3. The condenser as claimed in claim 1, wherein, during a time range, each of the pistons and associated cylinders being constructed for a same number of cylinder operating cycles as a high-pressure stage or as a low-pressure stage.
 4. The condenser as claimed in claim 1, further comprising a pre-compression cooler arranged downstream of the at least one low-pressure stage and upstream of the at least one high-pressure stage.
 5. The condenser as claimed in claim 1, wherein the valve has a rotatable cylindrical valve body.
 6. The condenser as claimed in claim 1, wherein the valve device is one of pneumatically, electrically or hydraulically switchable.
 7. The condenser as claimed in claim 1, wherein: the at least one high-pressure stage includes one high-pressure stage and the at least one low-pressure stage includes three low-pressure stages; and the at least two pistons include four pistons to form the one high-pressure stage and the three low-pressure stages.
 8. A compressor comprising a multistage condenser having: at least one high-pressure stage and at least one low-pressure stage; at least two pistons, which are driven via a common crankshaft supported in a crankcase, and which are guided in associated cylinders, and which form the at least one high-pressure stage and the at least one low-pressure stage; a line arrangement which communicates with the each of the cylinders for supplying and discharging air to and from the cylinders; wherein there is arranged in the line arrangement a switchable valve, which is constructed in such a manner that the at least one high-pressure stage depending on a switching position of the valve is associated with a different one of the cylinders.
 9. An operating method of a multistage condenser having at least one high-pressure stage and at least one low-pressure stage, at least two pistons driven by a common crankshaft supported in a crankcase and guided in associated cylinders to form the at least one high-pressure stage and the at least one low-pressure stage, and a line arrangement communicating with each of the cylinders for supplying and discharging air to and from the cylinders, the method comprising: switching a valve of the multistage condenser into a position in which at least one high-pressure stage of the multistage condenser is associated with one of at least two cylinders such that the at least one high-pressure stage moves the one of at least two cylinders further for each cylinder operating cycle.
 10. The condenser as claimed in claim 2, wherein, during a time range, each of the pistons and associated cylinders being constructed for a same number of cylinder operating cycles as a high-pressure stage or as a low-pressure stage.
 11. The condenser as claimed in claim 2, further comprising a pre-compression cooler arranged downstream of the at least one low-pressure stage and upstream of the at least one high-pressure stage.
 12. The condenser as claimed in claim 2, wherein the valve has a rotatable cylindrical valve body.
 13. The condenser as claimed in claim 2, wherein the valve device is one of pneumatically, electrically or hydraulically switchable.
 14. The condenser as claimed in claim 2, wherein: the at least one high-pressure stage includes one high-pressure stage and the at least one low-pressure stage includes three low-pressure stages; and the at least two pistons include four pistons to form the one high-pressure stage and the three low-pressure stages.
 15. The compressor as claimed in claim 8, wherein the at least one high-pressure stage for each cylinder operating cycle or each switching position moves one cylinder further.
 16. The compressor as claimed in claim 8, wherein, during a time range, each of the pistons and associated cylinders being constructed for a same number of cylinder operating cycles as a high-pressure stage or as a low-pressure stage.
 17. The compressor as claimed in claim 8, further comprising a pre-compression cooler arranged downstream of the at least one low-pressure stage and upstream of the at least one high-pressure stage.
 18. The compressor as claimed in claim 8, wherein the valve has a rotatable cylindrical valve body.
 19. The compressor as claimed in claim 8, wherein the valve device is one of pneumatically, electrically or hydraulically switchable.
 20. The compressor as claimed in claim 8, wherein: the at least one high-pressure stage includes one high-pressure stage and the at least one low-pressure stage includes three low-pressure stages; and the at least two pistons include four pistons to form the one high-pressure stage and the three low-pressure stages. 